Look before you soak: Are hot tubs safe?

The last thing you probably want to think about when stepping into a hot tub is what germs may be lurking beneath the bubbles.

While the water may feel boiling hot, the temperature is not high enough to kill bacteria that cause Pseudomonas, also known as "hot-tub rash," according to The Wall Street Journal. Bacteria can also cause more severe illnesses such as Legionnaires’ disease, an extreme form of pneumonia, Jonathan Yoder, an epidemiologist at the Centers for Disease Control and Prevention, told the newspaper.

Add people to the mix, and the germs multiply:

"The average bather has about a tenth of a gram of feces in his gluteal fold, which is a nice way of saying 'butt crack,'" Charles Gerba, Ph.D., a professor of microbiology and environmental studies at The University of Arizona, told The Huffington Post. With five people, "you have a tablespoon of poop in the hot tub," he said.

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There is a splash of good news, though. Only 16 outbreaks related to hot tubs were "reported to the CDC in 2009-2010 — 43.8 percent of them were suspected or confirmed to be caused by Pseudomonas, and 25 percent were confirmed to be caused by Legionella," The Huffington Post reported.

Also, hot-tub lovers don't need to guess when it's safe to soak. We've rounded up a list of expert tips on what to do before you take a dip:

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Make sure there is an optimum level of disinfecting chemicals. “If they use chlorine, you should look for a value of between 2 and 4 parts per million, and if they are using bromine, which is a similar disinfectant but lasts longer in hot temperatures, you’d look for a value between 4 and 6 parts per million,” Yoder said. Those values, along with recirculation and filter cleanliness, should be checked at least twice a day – and ideally, posted near the tub.

Take a shower. If soakers haven't showered before hopping in, the disinfectant in the tub may get watered down: lotion, makeup and sunscreen are magnets for the chemicals, according to Gerba. Three people is enough to make the disinfectant level drop, he said.

Make sure the water is clear. Turn the jets off, and make sure the water is not murky. “If you can’t see the bottom, that is not a good sign,” Yoder said.

Check for slime. It's an indication of not enough disinfectant, according to The Wall Street Journal.

Do a smell test. Do you smell that "chlorine smell"? It could be a sign of urine contamination, according to The Huffington Post, or a maintenance problem, according to the Centers for Disease Control and Prevention.

Listen up. You should be able to hear the pumps and filtration systems humming, according to the CDC.

Test the hot tub yourself. If you're still unsure, you can buy test strips at a pool-supply store. "You just dip them into the water before you get in," Michele Hlavsa, epidemiologist and chief of healthy swimming for the Centers for Disease Control of Prevention, told The Huffington Post. "The pads change colors and by the different colors you can judge the different disinfectant."

And, it probably goes without saying by this point, but always avoid getting the water in your mouth.